U.S. patent application number 15/003714 was filed with the patent office on 2016-05-19 for method and apparatus for supporting a floating roof disposed in a storage tank.
The applicant listed for this patent is DAVID BUSH. Invention is credited to DAVID BUSH.
Application Number | 20160137405 15/003714 |
Document ID | / |
Family ID | 55961047 |
Filed Date | 2016-05-19 |
United States Patent
Application |
20160137405 |
Kind Code |
A1 |
BUSH; DAVID |
May 19, 2016 |
METHOD AND APPARATUS FOR SUPPORTING A FLOATING ROOF DISPOSED IN A
STORAGE TANK
Abstract
Method and apparatus for cribbing a floating roof included in a
storage tank whereby a first and a first opposite force are applied
between a floor in the storage tank and an internal surface of the
floating roof. An additional set of forces are also provided and
are constrained according to the first and first opposite force,
not only in magnitude, but in position. By constraining these
forces to be applied orthogonally to the floating roof, horizontal
shear forces can be resisted thus reducing the likelihood of
failure of a cribbing unit.
Inventors: |
BUSH; DAVID; (UPLAND,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BUSH; DAVID |
UPLAND |
CA |
US |
|
|
Family ID: |
55961047 |
Appl. No.: |
15/003714 |
Filed: |
January 21, 2016 |
Current U.S.
Class: |
248/354.5 ;
248/351; 248/354.1 |
Current CPC
Class: |
B65D 88/40 20130101 |
International
Class: |
B65D 88/40 20060101
B65D088/40; F16M 11/24 20060101 F16M011/24 |
Claims
1. A method for supporting a floating roof disposed in a tank
wherein the floating roof includes an internal surface ordinarily
planar to a floor included in the tank: applying a first force to
the internal surface of the floating roof; applying a first
opposite force to the floor wherein the first opposite force is
substantially equal in magnitude to the first force; adjusting the
distance between the applied first force and the first opposite
force according to a desired distance between the floor and the
internal surface; applying a second force to the internal surface
of the floating roof; applying a second opposite force to the floor
wherein the second opposite force is substantially equal in
magnitude to the second force; constraining the distance between
the applied second force and the second opposite force according to
the adjusted distance between the applied first force and the first
opposite force; and resisting a horizontal force proximate to the
internal surface of the floating roof.
2. The method of claim 1 further comprising: applying a third force
to the internal surface of the floating roof; applying an third
opposite force to the floor wherein the third opposite force is
substantially equal in magnitude to the third force; and
constraining the distance between the applied third force and the
third opposite force according to at least one of the adjusted
distance between the applied first force and the first opposite
force and the adjusted distance between the applied second force
and the second opposite force.
3. The method of claim 1 further comprising: disposing the first
and second applied forces so that a planar that is substantially
coincident with their force vectors is substantially orthogonal to
an imaginary radial line of the floating roof.
4. The method of claim 1 further comprising: constraining the
application of the first force and the second force such that the
direction of application of the first force and the second force is
substantially orthogonal to a planar defined by the floating
roof.
5. The method of claim 1 further comprising: constraining the
distance between the applied first force and the first opposite
force to be substantially less than or equal to the distance
between the applied first force and the applied second force.
6. The method of claim 1 further comprising: preventing a
substantial discharge of an electrical arc from a physical member
applying the first force to at least one of the floor and the
internal surface of the floating roof.
7. The method of claim 1 further comprising: enabling the first
opposite force to be moved along the floor when the first force
applied to the internal surface of the roof falls below a
pre-established value.
8. A cribbing system comprising: first and second base members
comprising: receptacle for a vertical riser; receptacle for a
horizontal base span; first and second capping members comprising:
receptacle for a vertical riser; receptacle for a horizontal cap
span; horizontal base span intended to be received by the
horizontal base span receptacles included in the first and second
base; cap span intended to be received by the cap base span
receptacles included in the first and second capping members; first
riser intended to be received by the vertical riser receptacle
included in the first base member and the first cap member; and
second riser intended to be received by the vertical riser
receptacle included in the second base member and the second cap
member.
9. The system of claim 8 wherein the first and second risers
include a plurality of length adjustment restraints and wherein the
first and second base members and the first and second cap members
include at least one of a corresponding length adjustment
restraint.
10. The system of claim 8 wherein the first and second risers are
tubular along their length and further include holes set orthogonal
to the length of said risers and said holes penetrate a first wall
of said tube and a second wall of said tube.
11. The system of claim 8 further comprising: third horizontal base
span and wherein the first and second base members further comprise
a second base span receptacle, said second base span receptacle
being set at an angle of substantially equal to 60 degrees relative
to the first base span receptacle; third horizontal cap span and
wherein the first and second cap members further comprise a second
cap span receptacle, said second cap span receptacle being set at
an angle of substantially equal to 60 degrees relative to the first
base span receptacle; third base member comprising: receptacle for
a vertical riser, first receptacle for a horizontal base span; and
second receptacle for a horizontal base span set at an angle of
substantially 60 degrees relative to the first base span
receptacle; third cap member comprising: receptacle for a vertical
riser; first receptacle for a horizontal cap span; and second
receptacle for a horizontal cap span set at an angle of
substantially 60 degrees relative to the first cap span receptacle;
and third riser intended to be received by the vertical riser
receptacle included in the third base member and the third cap
member.
12. The system of claim 8 wherein the a length for the first and
second risers is substantially less than a length for the first
base span and the first cap span, wherein the lengths of the first
base span and the first cap span are substantially similar and the
lengths of the first and second risers is substantially
similar.
13. The system of claim 8 wherein the first and second base
members, the first and second capping members, the first riser, the
first base span and the first cap span are electrically conductive
further comprising a grounding strap, that includes a quick-attach
connector on a first end, and where a second end of said grounding
strap is attached to at least one of the first and second base
members, the first and second capping members, the first riser, the
first base span and the first cap span.
14. The system of claim 8 wherein the first and second base members
further comprise: first cross-brace attachment disposed proximate
to an interface between the riser receptacle and the horizontal
base span receptacle wherein the first and second cross-brace
attachment is in-line with said horizontal base span
receptacle.
15. The system of claim 8 wherein the first and second capping
members further comprise: first cross-brace attachment disposed
proximate to an interface between the riser receptacle and the
horizontal cap span receptacle wherein the first cross-brace
attachment is in-line with said horizontal cap span receptacle.
16. The system of claim 8 wherein the first and second base members
further include a ball transfer unit disposed opposite the riser
receptacle and wherein said the ball of said ball transfer unit is
forced against the floor of the tank when a downward force, which
is substantially collinear with the ball transfer unit, falls below
a pre-established threshold.
17. An apparatus for supporting a floating roof in a storage tank
comprising: means for applying a first force to the internal
surface of the floating roof; means for applying a first opposite
force to the floor wherein the first opposite force is
substantially equal in magnitude to the first force; means for
adjusting the distance between the applied first force and the
first opposite force according to a desired distance between the
floor and the internal surface; means for applying a second force
to the internal surface of the floating roof; means for applying a
second opposite force to the floor wherein the second opposite
force is substantially equal in magnitude to the second force; and
means for constraining the distance between the applied second
force and the second opposite force according to the adjusted
distance between the applied first force and the first opposite
force.
18. The apparatus of claim 17 further comprising: means for
applying a third force to the internal surface of the floating
roof; means for applying an third opposite force to the floor
wherein the third opposite means for force is substantially equal
in magnitude to the third force; and means for constraining the
distance between the applied third force and the third opposite
force according to at least one of the adjusted distance between
the applied first force and the first opposite force and the
adjusted distance between the applied second force and the second
opposite force.
Description
BACKGROUND
[0001] There are many situations where there is a need to support a
planar structure at variable distances in height to different
distances to lower some height above the ground. One such
application is that of a storage tank that includes a floating roof
structure. This example use case can be best described with
reference to FIG. 1. In FIG. 1, a floating roof structure 200 is
typically used where a storage tank 205 is used to store a liquid,
for example, jet fuel, gasoline, diesel, sour water and crude oil.
Hence, it is common place for such a storage tank to include such a
floating roof structure for environmental protection from flammable
and hazardous vapor omissions to the environment. It should be
appreciated that such a floating roof structure "floats" on top of
the liquid product stored in the storage tank. As the level of the
liquid product stored in the tank fluctuates, so does the height of
the floating roof structure relative to a floor included in such a
tank.
[0002] It is also a fact that an API 653 inspection is regulatory
mandated for above ground storage tanks every ten years. The
regulations require that all above ground storage tanks must be
inspected and repaired to API 653 standards to verify the
structural integrity of the tank shell, floating roof vapor control
integrity and the tank floor. The aim of such inspections is to
preclude seepage of hazardous, toxic and flammable liquids into the
ground. Such seepage may cause environmental impact with wide
reaching consequences, such as pollution of water tables. Because
such inspections are known to reveal the type and extent of repairs
needed to prevent leaks and other environmental cataclysms, it is
unlikely that any of these inspection requirements will ever be
abated. And, there are also occasions when the storage tank must be
cleaned in preparation for storing a different liquid produce or a
different class of a liquid product relative to a former substance
previously stored in the tank. The floating roof must be held above
the floor of the storage tank so that personnel can freely and
safely conduct themselves during all such inspection, repair and
cleaning activities.
[0003] FIG. 1 is a pictorial representation of a prior art
apparatus for supporting a floating roof when a storage tank is
devoid of liquid content. For years and years and years, the
process of supporting a floating roof in the absence of a liquid
product has been accomplished using substantially similar methods,
each of which rely on the use of substantially identical support
apparatus. As can be seen, the prior art has thus far relied on a
basic support method using a "cribbing stack".
[0004] A cribbing stack 210 is typically made up of alternating
layers of wood members, wherein each wood member from a preceding
layer is set orthogonal to a subsequent layer. Hence, the height of
the cribbing stack could be adjusted by simply stacking up more of
such alternating layers of wooden members. Up until now, this prior
art technique has been used without much deviation from this basic
concept, that being the use of alternating layers of wooden
members. It should be noted that these wooden members are someone
akin to common railroad ties that are readily available throughout
the world.
[0005] FIG. 1 also depicts one grave disadvantage associated with
the use of a wooden, layered cribbing stack. It is well settled
that a floating roof may exhibit rotational forces 215. When the
floating roof is first lowered and substantially all product is
removed from the tank, a collection of "legs", each of which
penetrates the floating roof, are used to support the floating
roof. These legs are very susceptible to horizontal forces that
each leg experiences when the roof begins to rotate. This is true
regardless of whether the storage tank is empty or of it has liquid
content.
[0006] Wind can induces such rotational movement of the floating
roof. There are methods to retard such rotational movement, but
these methods often fail. One such method is based on the use of
"anti-rotation wedges". These wedges are, by their very name,
disposed between an outer perimeter of the floating roof and an
internal wall of the storage tank. Such anti-rotational wedges are
scarcely effective in the face of sever rotational movement of the
floating roof.
[0007] It is when the floating roof exhibits rotational movement
that personnel working in a storage tack are most vulnerable to
injury and death. When a floating roof begins to rotate, it begins
to apply a moment force onto each leg. Now, as the legs begin to
fail, the plurality of cribbing stacks are intended to support the
floating roof at some minimum height necessary to keep all
personnel safe. Because the layers of a wooden cribbing stack are
not fastened to each other, the cribbing stack simply falls apart
when these horizontal forces go unopposed. The upper layers of the
cribbing stack, from a force perspective, simply shear away from
the lower layers of the cribbing stack. This, of course, results in
the type of total failure of the support structure that has cost
many lives and has resulted in extensive collateral, materiel
damage and environmental impact.
[0008] There are also several environmental issues associated with
the use of a wooden cribbing stack. In should be appreciated that
the product ordinarily stored in a storage tank is a liquid and
such liquids are typically hazardous materials. Such hazardous
material may include petro chemical products, crude oil, flammable
liquids and many other forms of extremely hazardous materials.
Residual product in the storage tank will ordinarily permeate the
wooden members. Hence, such contaminated wooden members cannot be
reused and must be discarded as horizontal waste. And, each time a
wooden member is discarded, new lumber must be used at the cost of
many trees, harvested from our forests, further impacting global
warming and greenhouse gas effects.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] Several alternative embodiments will hereinafter be
described in conjunction with the appended drawings and figures,
wherein like numerals denote like elements, and in which:
[0010] FIG. 1 is a pictorial representation of a prior art
apparatus for supporting a floating roof when a storage tank is
devoid of liquid content;
[0011] FIG. 2 is a flow diagram that depicts one example method for
supporting a planar structure, for example a floating roof in a
storage tank;
[0012] FIG. 3 is a flow diagram that depicts an alternative example
method that relies upon the application of a third set of
forces;
[0013] FIG. 4 is a flow diagram that depicts an alternative example
method for maximizing to amount of horizontal force that a cribbing
unit will resist;
[0014] FIG. 5 is a flow diagram that depicts one alternative
example method for resisting horizontal forces by applying the
first and second forces orthogonally to the floating roof;
[0015] FIG. 6 is a flow diagram that depicts one alternative
example method that reduces the likelihood of "tip over" by a
cribbing unit;
[0016] FIG. 7 is a flow diagram that depicts one alternative method
useful where product formerly stored in a storage tank is
volatile;
[0017] FIG. 8 is flow diagram that depicts an alternative example
method that provides for easier movement of a cribbing unit when it
is disposed in a storage tank;
[0018] FIG. 9 is a pictorial diagram of one example embodiment of a
cribbing unit that adheres to the method and techniques for
cribbing as described thus far;
[0019] FIG. 10 is a pictorial diagram of a cribbing unit that
includes enhanced horizontal resistance;
[0020] FIG. 11 is a cut-away pictorial of a storage tank wherein
the floating roof is supported by a plurality of new cribbing
units;
[0021] FIG. 12 depicts a typical layout of cribbing units under a
floating roof; and
[0022] FIG. 13 is a cross section view of a base member that
includes a roller transfer.
DETAILED DESCRIPTION
[0023] FIG. 2 is a flow diagram that depicts one example method for
supporting a planar structure, for example a floating roof in a
storage tank. According to this example method, a first force is
applied to an internal surface of a floating roof (step 5). In a
substantially contemporaneous step, a first substantially opposite
force is applied to the floor (step 10). According to this example
method, the distance between the applied first force and the
applied first opposite force is adjusted (step 15) according to a
particular height at which the floating roof is to be held above
the floor. It should be appreciated that, at first blush, these two
method steps can be accomplished by simply placing a load bearing
member, operating in compression, between the floating roof and the
floor. In such a simple method, a load bearing member is simply
used to the prop up the roof in order to hold it at a
pre-established height above the floor. But, even in this simple
embodiment, there is nothing provided to act against horizontal
forces imparted to a cribbing stack when the floating roof
rotates.
[0024] The present method goes further by requiring that a second
force is to be applied to the internal surface of the floating roof
(step 20) and a substantially equal, but opposite force is applied
to the floor (step 25). In one alternative example method, the
cribbing unit further causes the distance between the first and the
first opposite force and the second and the second opposite force
at distances substantially equal to each other (step 30). A last
step is then to resist horizontal forces applied proximate to the
first and second forces (step 32). The present method, when
applied, resists horizontal shear forces imparted upon a cribbing
unit by a rotational movement of the floating roof.
[0025] FIG. 3 is a flow diagram that depicts an alternative example
method that relies upon the application of a third set of forces.
In this alternative method, a third force is applied to the
internal surface of the roof (step 35) along with a third equal,
but substantially opposite third force is applied to the floor of
the storage tank (step 40). In one alternative example method, the
distance between the third and third substantial equal but opposite
force is constrained according to an adjusted distance between the
first and first opposite force (step 45). In yet another
alternative example method, the distance between the third and
third substantial equal but opposite force is constrained according
to an adjusted distance between the second and second opposite
force (step 50).
[0026] FIG. 4 is a flow diagram that depicts an alternative example
method for maximizing to amount of horizontal force that a cribbing
unit will resist. FIG. 12 is a plan view of placement of a
plurality of cribbing units according to this alternative example
method. As can be seen in FIG. 12, application of the first force
220 and the second force 225 is accomplished by setting a line
segment between the first force 220 and the second force 225 to be
substantially orthogonal 230 to a radial line 235. It should be
appreciated that, by setting these two forces substantially
orthogonal to the radial line 235 (step 55), this alternative
method further resists application of a horizontal force applied to
a cribbing unit by a rotating floating roof.
[0027] FIG. 5 is a flow diagram that depicts one alternative
example method for resisting horizontal forces by applying the
first and second forces orthogonally to the floating roof. One
aspect of resisting horizontal movement that may be imparted upon a
cribbing unit by a rotating floating roof provides for applying the
first and second forces in a direction substantially orthogonal to
a plane coincident with the planer of the floating roof.
[0028] Again in FIG. 2, method step 32, one possible embodiment of
the present illustrative method includes members to continuously
maintain such an orthogonal application of the first and second
forces. It can thus be appreciated that, by so constraining the
application of the first and second forces to the internal surface
of the roof, application of the first opposite but equal first
force and the second opposite, but equal second force are also
constrained in an orthogonal application to the floor of the tank.
Accordingly, such constraint of the first and first but opposite
force and the second and the second but opposite force will result
in resisting a horizontal force imparted upon a cribbing unit by
the floating roof as the floating roof exhibits rotation.
[0029] FIG. 6 is a flow diagram that depicts one alternative
example method that reduces the likelihood of "tip over" by a
cribbing unit. It should be appreciated that, according to one
illustrative use case, a cribbing unit may in fact tip over if the
distance between application of the first and second forces is
smaller than the application of the first and first substantially
opposite first force. Accordingly, this example method provides
that the distance between application of the first and first
opposite force should be held less than the distance between
application of the first and second forces (step 60). Hence, a
cribbing unit that exhibits such a constraining characteristic is
less likely to tip over when subjected to horizontal forces.
[0030] FIG. 7 is a flow diagram that depicts one alternative method
useful where product formerly stored in a storage tank is volatile.
It should be appreciated that, according to essentially all prior
art, cribbing stacks were utilized and that these cribbing stacks
were comprised of wood members. It should also be appreciated that
where there was volatile product stored in a storage tank, it is
imperative not to introduce an ignition source into the tank
volume. Since the prior art cribbing stacks were made of wood,
there was little likelihood that these wooden members would accept
a static charge. With the new cribbing units introduced here, there
is a potential for electrical discharge because the cribbing units
are made of various metals.
[0031] Accordingly, in this alternative method, it becomes
necessary to prevent, to as a great extent as possible, the amount
of static electrical charge that can be accepted by the cribbing
unit. As such, this alternative example method provides for
preventing a substantial discharge of static electricity from a
base member, included in a cribbing unit, to the tank floor(step
75). This alternative example embodiment further includes a step
for preventing a substantial discharge of static electricity from a
cap member, also included in one alternative embodiment of a
cribbing unit, to the internal surface of the floating roof (step
80). In should be appreciated that, according to one alternative
embodiment, these method steps are accomplished by using a braided
grounding element to make electrical contact from the cribbing unit
to at least one of the tank floor and the internal surface of the
floating roof.
[0032] FIG. 8 is flow diagram that depicts an alternative example
method that provides for easier movement of a cribbing unit when it
is disposed in a storage tank. Prior art methods for cribbing
relied on wooden members that were stacked together to form a
cribbing stack. It should be appreciated that any relocation of the
cribbing stack would require extensive labor in order to tear down
the cribbing stack and reassemble it in another location in the
storage tank. Hence, the weight of the cribbing stack, per se, was
not an issue for relocating the cribbing stack. The individual
members of the cribbing stack could easily be moved by repair and
support technicians and reassembled into a cribbing stack in a new
location.
[0033] With the advent of the cribbing units now available,
movement of the cribbing units becomes problematic because the
cribbing units, which are ideally moved as whole units, are heavy
and require great physical effort in order to lift and move them to
a new location. Of course, a cribbing unit could be torn down into
its constituent components, but that again leaves personnel
vulnerable to failure of the legs provided by the floating roof to
support the floating roof when the tank is devoid of product.
Hence, it is preferable to move the cribbing units "intact" from
one location to another within the volume of the storage tank. In
this alternative example method, movement of the first force is
facilitated (step 95) when the force applied to the floating roof
is less than a pre-established threshold (step 90).
[0034] FIG. 9 is a pictorial diagram of one example embodiment of a
cribbing unit that adheres to the method and techniques for
cribbing as described thus far. It should be appreciated that the
new cribbing unit is typically described as a system for cribbing
because various components in the system may or may not be utilized
depending on specific use cases. Accordingly, even though most of
this description described a "cribbing unit", the claims appended
hereto refer to a system for cribbing because of the modular nature
of the cribbing system.
[0035] In this example embodiment, a cribbing unit comprises first
and second base members (130 and 140). Each such base member
includes a receptacle 145 for a vertical riser 150. This embodiment
further includes a first and second vertical riser (150 and 155).
It should be appreciated that each of said vertical risers are
tubular in nature and are accepted by the receptacles 145 included
in each of the first and second base members (130 and 140). The
first vertical riser 150 is "pinned" into position so as to
constrain the distance between a first force 220 and a first
opposite force 225. Likewise, the second vertical riser 155 is
pinned into position so as to constrain the distance between a
second force 230 and a second opposite force 235.
[0036] In this example embodiment, the first and second base
members (130 and 140) also include a receptacle for a horizontal
base span 170. The base span 170 is also included in this example
embodiment and is received by the receptacles included in the first
and second base members (130 and 140). Typically, the horizontal
base span is "pinned" into position so that it constrains the
distance between a first opposite force 225 and a second opposite
force 235 as applied to the internal surface of the floating
roof.
[0037] This example embodiment also includes a first cap member 170
and second cap member 175. Each of said cap members also includes a
receptacle for a vertical riser 180 and a receptacle for a
horizontal cap span 185. In application, each cap member receives a
vertical riser (150 and 155) and a horizontal cap span 190. It
should be appreciated that the horizontal cap span is pinned into
position so as to restrain the distance between the first force 220
and the second force 230. Likewise, the vertical risers (150 and
155) are also pinned into the cap members (170 and 175). In
application of the present apparatus, the vertical risers 150 and
155 are pinned at substantially similar locations so that the
distance between the application of the second force 230 and the
second opposite force 235 is constrained to be substantially equal
to the distance between the first force 220 and the first opposite
force 225.
[0038] FIG. 9 also depicts an alternative embodiment where the
height of the cribbing unit is adjustable. In order to achieve
adjustment, the receptacles for receiving the risers 180 included
in each of the base members and cap members includes restraint
positions comprising a hole 195 that penetrates both walls of a
tubular receptacle. The risers (150 and 155) also include
corresponding holes 197 through a first and second wall of a
tubular riser. In this alternative embodiment, holes are provided
at one or at both ends of the risers (150 and 155).
[0039] FIG. 9 presents yet another alternative embodiment where
three forces are used in support of a floating roof. In this
alternative embodiment, a third vertical riser 275 is included in
the cribbing unit. This third vertical riser 275 is used in
conjunction with a third cap member 285 and a third base member
295. Two additional cap spans 305 and two additional base spans 310
are used to constrain position and application of a third force 315
and a third opposite force 320 relative to at least one of the
position of the first force 220 and the position of the second
force 230. In this alternative embodiment, the height of the
cribbing unit at the third riser is set to be substantially equal
to the height of the cribbing unit at the first 220 or second 230
forces.
[0040] FIG. 9 also shows a cribbing unit that resists "tip-over".
In this alternative embodiment, the length of the horizontal cap
span 190 and the horizontal base span 170 is greater than the
overall height of the cribbing unit 400 itself, which is driven by
the length of the vertical risers. Since the cribbing unit 400 is
wider than it is tall, it resists tip-over when a horizontal force
is applied proximate to the application of any of the first 220 and
second 230 forces.
[0041] FIG. 10 is a pictorial diagram of a cribbing unit that
includes enhanced horizontal resistance. In this alternative
embodiment, a cribbing unit further includes diagonal cross-braces
250. In this alternative embodiment, across brace is attached at
its ends to a cross-brace attachment included in a cap member and
to across-brace attachment included in abuse member wherein the cap
and base members are diagonal to each other. It can be appreciated
that these cross-braces 250 operate in tension when the cribbing
unit experiences horizontal force.
[0042] FIG. 11 is a cut-away pictorial of a storage tank wherein
the floating roof is supported by a plurality of new cribbing
units. This figure depicts a storage tank 205 that includes a metal
floor 203. There is a plurality of cribbing units 400 depicted
where the cribbing units are arranged to support a floating roof
200 in the event the legs ordinarily used to support the floating
roof 200 should fail.
[0043] It can be appreciated that, according to an alternative
embodiment, the new cribbing units are constructed from tubular
metal. Various metals can be used to fashion the new cribbing
units. For example, one alternative embodiment provides for
constructing the new cribbing units from at least one of a titanium
and a titanium alloy. In another example embodiment, the new
cribbing units are constructed from steel. The advantages of
constructing the new cribbing unit from metal are multifold. First,
a metal cribbing units is able to bear much greater compression
loads than the wooden cribbing stack of prior art. As such, a fewer
number of the new cribbing units are needed to support a floating
roof.
[0044] From an environment perspective, a cribbing system
constructed from metal does not need to be discarded as does a
wooden cribbing stack of prior art. A metal used to construct the
cribbing units will not absorb hazardous materials and can be
easily cleaned while the floor of the storage tank is being
cleaned. All hazardous material can be contained in such cleaning
process. And, because the cribbing system herein described can be
reused, our forests need not lay down their lives to provide new
cribbing material.
[0045] FIG. 12 depicts a typical layout of cribbing units under a
floating roof. It can be appreciated that cribbing units no longer
need to be stacked in a particular place. A much safer method of
placing the new cribbing unit is to assemble a cribbing unit and
glide it into position.
[0046] FIG. 13 is a cross section view of a base member that
includes a roller transfer. In order to facilitate movement of a
cribbing unit along the tank floor, one alternative embodiment of a
cribbing unit includes a spring loaded roller transfer 465. This
alternative embodiment also includes a spring 450 that is selected.
to cause the roller transfer unit 465 to extend downward against a
floor surface. When a force 470 exceeds the spring force, then the
roller transfer unit 465 retracts back into the receptacle 145 for
the vertical riser, except that the roller transfer unit 465
retracts back into the receptacle 145 at an end opposite the
vertical riser. When the spring 450 is not compressed, the roller
transfer unit 465 makes contact with the floor and enables easy
movement of the cribbing unit along the floor. When the load
bearing down on the cribbing units is great enough so as to
compress the spring, then the roller transfer retracts into the
base member and the load is supported by the outer perimeter of the
base member 145.
[0047] FIG. 13 also depicts that a base member, or a cap member,
further includes a grounding element. The grounding element 490
makes contact with either the floor or the internal surface of the
floating roof so that the voltage on the cribbing unit, which is
entirely conductive, remains at ground. In one example embodiment,
the grounding element 490 comprises a broom-like structure made of
braided wire.
[0048] While the present method and apparatus has been described in
terms of several alternative and exemplary embodiments, it is
contemplated that alternatives, modifications, permutations, and
equivalents thereof will become apparent to those skilled in the
art upon a reading of the specification and study of the drawings.
It is therefore intended that the true spirit and scope of the
claims appended hereto include all such alternatives,
modifications, permutations, and equivalents.
* * * * *